1. Field of the Invention
The present invention relates to a heat exchanger, such as a condenser for use in an automotive air conditioning system.
2. Description of the Prior Art
Japanese Utility Model Application publication No. 63-142,586 discloses a heat exchanger, such as a condenser for use in an automotive air conditioning system as illustrated in FIGS. 1 and 2.
The condenser includes a plurality of adjacent, essentially flat tubes 10 each having a flat oval cross-section and a pair of open ends which allow refrigerant fluid to flow therethrough. Each flat tube 10 includes upper and lower flat surfaces 101 which are disposed in planes parallel to the direction of air flow as indicated by arrow "A", and opposite curved surfaces 102. One of opposite curved surfaces 102 connects one end of upper flat surface 101 with one end of the lower flat surface 101 and the other of opposite curved surfaces 102 connects the other end of upper flat surface 101 with the other end of lower flat surface 101. A plurality of corrugated fin units 12 are disposed between adjacent flat tubes 10. Each flat tube 10 includes a plurality of vertical partition walls 11 which are integrally formed on an inner surface of each flat tube 10. Vertical partition walls 11 are formed along the longitudinal axis of flat tubes 10 and divide the interior of flat tubes 10 into a plurality of longitudinally extending chambers. Corrugated fin units 12 are brazed to flat tubes 10 to form heat exchange region 100 as discussed below.
A pair of cylindrical header pipes 120 and 140 each having opposite open ends are disposed perpendicular to flat tubes 10 and may have, for example, a clad construction. The opposite open ends of header pipes 120 and 140 are fixedly and hermetically plugged by respective caps 121, 122, 141, and 142 by brazing. Plate 110, having a generally U-shaped cross-section, is fixedly disposed on an upper end of heat exchange region 100. The ends of plate 110 are fixedly connected to an inside region of an outer peripheral surface of the upper-most portion of header pipes 120 and 140 by brazing. Plate 111, also having a generally U-shaped cross-section, is fixedly disposed on a lower end of heat exchange region 100. The ends of plate 111 are fixedly connected to the inside region of an outer peripheral surface of the lowermost portion of header pipes 120 and 140 in the same manner as plate 110. Plates 110 and 111 reinforce the structural strength of the condenser.
Opening 123, having a diameter slightly greater than the outer diameter of inlet pipe 22, is formed at an upper portion of header pipe 120. After the termination of the brazing process, one end of cylindrical inlet pipe 22 is inserted into opening 123 and is then fixedly and hermetically connected thereto, for example, by a further brazing process. Inlet pipe 22 is provided with a conventional union joint (not shown) at the other end thereof.
An opening (not shown), having a diameter slightly greater than the outer diameter of outlet pipe 23, is formed at a lower portion of header pipe 140. One end of cylindrical outlet pipe 23 is inserted into the opening and is then fixedly and hermetically connected thereto in the same manner as inlet pipe 22. Inlet pipe 22 and outlet pipe 23 protrude from header pipes 120 and 140, respectively, in opposite directions. Inlet pipe 22 and outlet pipe 23 protrude in a plane perpendicular to the flow of air through heat exchange region 100.
Referring to FIGS. 3-5, a plurality of slots 124 having oval cross-sections are formed at equal intervals on an inner side of each of header pipes 120 and 140. The sizes of slots 124 is slightly greater than the outer sizes of flat tubes 10. The condenser is temporarily assembled by inserting the opposite longitudinal ends of each of flat tubes 10 into the interior of header pipes 120 and 140 through slots 124. The penetration of the longitudinal ends of flat tubes 10 terminates at approximately one-third of the diameter of an inner periphery of the header pipes as illustrated in FIG. 5. The flat tubes, the fin units, the header pipes, the caps, and the plates are all temporarily assembled with one another at the same time.
After the assembling process of the condenser is completed, the temporarily assembled condenser is transported from an assembly line to a furnace in which a brazing process is carried out. As a result of this transportation of the temporarily assembled condenser, the flat tubes 10 slide undesirably relative to header pipes 120 and 140 through slots 124. Therefore, when the brazing process of the condenser is completed, defects in the condenser may have occurred. The longitudinal ends of flat tubes 10 may have been disengaged from slots 124 or the brazed condenser may have a non-standard configuration because of the relative sliding of flat tubes 10.
In order to prevent the undesirable relative sliding motion between the flat tubes and the header pipes through the slots, it is known to use a fastening tool which is temporarily attached to the temporarily assembled condenser so as to firmly fasten the flat tubes and the header pipes to each other. The fastening tool is detached from the condenser after completion of the brazing process. However, the steps of attaching the fastening tool to the temporarily assembled condenser and detaching the fastening tool from the brazed condenser after completion of the brazing process complicates the manufacturing process of the condenser. Hence, the efficiency of manufacturing the condenser is decreased. Furthermore, the provision of the fastening tool increases the manufacturing costs of the condenser.